I do not have a solution to suggest. However, I’d offer my opinion/observation that we rarely achieve full utilization of the CPU running X-Plane; and the FPS that you’re experiencing is not unexpected. While only an X-Plane software developer can give you a qualified explanation on the utilization.

The low GPU loading shown is indicative of the system being CPU-bound running under your current settings. The settings on the right side of Graphics Settings page (i.e. World Objects and Reflection) have the most impacts on the CPU, while those settings on the left side (Visual Effects etc.) demand power from the GPU. So by lowering the “Number of World Objects”, you might see an increase on GPU utilization, because bandwidth from the CPU may now be diverted into keeping the GPU busier. The FPS may benefit as a result of higher overall utilization.

You system spec is good, but not high end. With X-Plane being X-Plane, and to run at high graphics settings, the first thing comes to my mind on boosting the FPS is by upgrading to a higher GHz CPU. More RAM may also be needed.

It is well known within the X-Plane flight sim fraternity that AMD CPUs and GPUs do not give the best performance. When Vulkan is introduced into X-Plane (when ?) there should be an improvement for AMD products.